From: Sebastian Andrzej Siewior <bigeasy@linutronix•de>
To: Yannick Vignon <yannick.vignon@oss•nxp.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st•com>,
Alexandre Torgue <alexandre.torgue@foss•st.com>,
Jose Abreu <joabreu@synopsys•com>,
"David S. Miller" <davem@davemloft•net>,
Jakub Kicinski <kuba@kernel•org>,
Maxime Coquelin <mcoquelin.stm32@gmail•com>,
Eric Dumazet <edumazet@google•com>,
Antoine Tenart <atenart@kernel•org>,
Alexander Lobakin <alexandr.lobakin@intel•com>,
Paolo Abeni <pabeni@redhat•com>, Wei Wang <weiwan@google•com>,
Kumar Kartikeya Dwivedi <memxor@gmail•com>,
Yunsheng Lin <linyunsheng@huawei•com>,
Arnd Bergmann <arnd@arndb•de>,
netdev@vger•kernel.org, Vladimir Oltean <olteanv@gmail•com>,
Xiaoliang Yang <xiaoliang.yang_1@nxp•com>,
mingkai.hu@nxp•com, Joakim Zhang <qiangqing.zhang@nxp•com>,
sebastien.laveze@nxp•com, Yannick Vignon <yannick.vignon@nxp•com>
Subject: Re: [PATCH net-next 1/2] net: napi: wake up ksoftirqd if needed after scheduling NAPI
Date: Thu, 3 Feb 2022 20:41:58 +0100 [thread overview]
Message-ID: <YfwwBvO2+xVjer/+@linutronix.de> (raw)
In-Reply-To: <20220203184031.1074008-1-yannick.vignon@oss.nxp.com>
On 2022-02-03 19:40:30 [+0100], Yannick Vignon wrote:
> From: Yannick Vignon <yannick.vignon@nxp•com>
>
> If NAPI was not scheduled from interrupt or softirq,
> __raise_softirq_irqoff would mark the softirq pending, but not
> wake up ksoftirqd. With force threaded IRQs, this is
> compensated by the fact that the interrupt handlers are
> protected inside a local_bh_disable()/local_bh_enable()
This is not compensated but one of the reasons why it has been added.
> section, and bh_enable will call do_softirq if needed. With
> normal threaded IRQs however, this is no longer the case
> (unless the interrupt handler itself calls local_bh_enable()),
Exactly.
> whic results in a pending softirq not being handled, and the
> following message being printed out from tick-sched.c:
> "NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x!!!\n"
Yes. This also includes various other call sites.
> Call raise_softirq_irqoff instead to make sure ksoftirqd is
> woken up in such a case, ensuring __napi_schedule, etc behave
> normally in more situations than just from an interrupt,
> softirq or from within a bh_disable/bh_enable section.
I would suggest to add a bh dis/en around the function that is known to
raise BH. This change to ____napi_schedule() as you suggest will raise
ksoftirqd and is not what you want. What you want is to process NAPI in
your current context.
> Signed-off-by: Yannick Vignon <yannick.vignon@nxp•com>
Sebastian
prev parent reply other threads:[~2022-02-03 19:42 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 18:40 [PATCH net-next 1/2] net: napi: wake up ksoftirqd if needed after scheduling NAPI Yannick Vignon
2022-02-03 18:40 ` [PATCH net-next 2/2] net: stmmac: move to threaded IRQ Yannick Vignon
2022-02-03 19:08 ` [PATCH net-next 1/2] net: napi: wake up ksoftirqd if needed after scheduling NAPI Eric Dumazet
2022-02-03 23:40 ` Yannick Vignon
2022-02-03 23:57 ` Eric Dumazet
2022-02-04 1:09 ` Jakub Kicinski
2022-02-04 8:19 ` Sebastian Andrzej Siewior
2022-02-04 15:43 ` Jakub Kicinski
2022-02-04 17:15 ` Yannick Vignon
2022-02-04 17:36 ` Jakub Kicinski
2022-02-04 17:45 ` Jakub Kicinski
2022-02-04 18:03 ` Sebastian Andrzej Siewior
2022-02-04 18:50 ` Jakub Kicinski
2022-02-04 18:52 ` Jakub Kicinski
2022-02-08 11:51 ` Sebastian Andrzej Siewior
2022-02-08 15:35 ` Jakub Kicinski
2022-02-08 17:45 ` Sebastian Andrzej Siewior
2022-02-09 0:16 ` Jakub Kicinski
2022-02-08 15:57 ` Paolo Abeni
2022-02-08 18:21 ` Sebastian Andrzej Siewior
2022-02-09 11:26 ` Marc Kleine-Budde
2022-02-03 19:41 ` Sebastian Andrzej Siewior [this message]
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